Stemness genes (Nanog, Oct4 and Sox2) and C-X-C chemokine receptor 4 (CXCR4) have important roles in maintaining CSC signaling and stemness in drug-resistant cancer cells.11,26 As expected, stemness-related factors such as Nanog, Oct4, Sox2 and CXCR4 were overexpressed in A549/PTX cells (Figure 1f). This evidence concerns the gene SOX2 and cancer.